There are not many places where you can learn the history behind the name of the Jesus Christ lizard and see why a roller-coaster speeds so quickly downhill.

MOLLY DRISCOLL

There are not many places where you can learn the history behind the name of the Jesus Christ lizard and see why a roller-coaster speeds so quickly downhill.

But in two new exhibits at the Museum of Science in Boston, "Reptiles: The Beautiful and the Deadly" (the second part of which sounds like ABC's newest soap opera) and "K'Nex: Building Thrill Rides," visitors can come face-to-face with giant lizards, snakes and alligators and create anything they can think of by connecting thin plastic rods, wheels and other components.

Go to the left when you enter the exhibit area and you're in reptile country, a dimly lit room with lots of glass walls behind which lurk scaly animals. The right side of the room is dedicated to turtles and lizards, and one of the first creatures you'll meet is the star tortoise, which has a huge spiky shell that provides camouflage in the wild.

You can test your turtle knowledge with true-or-false questions. "Some turtles have antifreeze in their blood" was surprisingly true: They produce glycogen to keep themselves from freezing. There's a large model of a tortoise shell that could be a comfortable seat even for an adult, and, next to it, a sign giving facts about giant tortoises, how big they can grow (more than 500 pounds), and how long they can live (more than 100 years, but any kid who's seen "Finding Nemo" could tell you that). Be sure to check out the alligator snapping turtle a little farther along the wall, a turtle so huge it's hard to believe he belongs to the same species as the pet you may keep in your terrarium. An indicator of its size? As evidenced by its name, it sometimes eats small alligators.

On this side of the reptile exhibit, you also can see a variety of lizards, including the frilled leaf-tail gecko that during one visit was stuck flat against the display case. Check out the bearded dragon, which frightens off enemies by stretching the skin under the chin and making its scales stick out, and the gila monster, which eats only a few meals per year, an adaptation that helps it survive in harsh desert climates.

In the middle of the exhibit are a crocodile and an American alligator. You can tell the species apart by comparing snout sizes on skulls hanging on the wall. Next to the crocodile is an interactive station where you can hear sounds made by crocodiles for various situations, including calls for help and threats like "You're invading my territory." Most sound like coughs or hisses.

Ready for reptiles without any legs? The left side of the exhibit is dominated by snakes, which can range from a few inches to 20 feet long. You can see the rattlesnake, which forms its distinctive rattle by shedding its skin and shaking it when it gets nervous, and the Pueblan milk snake, which lives in habitats from Canada to South America. Other varieties on display include a cottonmouth, a rat snake and a green tree python. If you flip up wooden squares on one part of the wall, you can get answers to such questions as "What is the fastest snake?" (the mamba, which can move up to 7 mph) and "What is the heaviest snake?" (the anaconda, which can weigh as much as 400 pounds). Check out cool displays like a snake skull that retracts its fangs with the press of a button, and a snake head slowly dripping liquid into a glass, showing how a snake would be milked of venom to provide a cure for snakebite. (Turns out the cure for most snake bites is the venom plus antibodies built up against the venom, taken from a horse.) Near the snakes, there are wooden benches and a video playing "Reptiles: The Beautiful and the Deadly" that restarts every few minutes. It relates intriguing factoids such as how a larger shell helps turtles cool off and how crocodiles protect their eyes underwater.

It goes without saying that anyone who's not a fan of reptiles should skip the exhibit, but for those who can't get enough, you can lean right up against the glass holding the slithery creatures to get as close as possible — and if you're lucky, you might happen upon a staff member holding a snake or lizard who can tell you what its species name means and other facts about the animal. If you have younger children, keep in mind that some explanations, such as how a snake constricts prey, and a large section on varieties of snake venom, may be a little scary for some.

If younger visitors are ready to blow off some steam, the K'Nex exhibit will be a good next stop. On either side of the room are tables where children and adults can sit and build using K'Nex — long, thin rods of plastic that can connect. Around the edges of the room are giant models, built using K'Nex, of thrill rides you might find at a carnival, including a carousel. The science aspect of the exhibit comes into play with small timers next to each ride that invite you to count how many revolutions it makes per minute.

One wall placard explains the invention of the Ferris wheel (created by George G. Ferris, who scribbled the design on a napkin and built it for the 1893 World's Fair). You can also learn how kinetic energy makes a roller-coaster car gain speed down a hill.

It's a fun area and you do learn about the science of thrill rides, but parts of the K'Nex exhibit promote the toy pretty heavily. Lumped in with the Ferris wheel history is the history of K'Nex, and large signs at the building tables tell you that you can buy your K'Nex creation, and list prices by weight. One wall of the room is dominated by an area selling K'Nex products.

These exhibits provide a fascinating and enriching way to spend a few hours at the museum.